The synaptic transmission mechanism at the cellular level and the information-processing mechanism of synaptic organization at the systems level are studied in normal and mutant Drosophila melanogaster. Development of the physiology of synapses in insects is an acute necessity. Its variety of synapses and many preparations promise fruitful study at both the cellular and systems level on a single preparation. Genetic techniques can also be used in combination with physiological techniques. This study will develop the physiology of both peripheral and central synapses in insect and introduce genetic techniques to neurophysiology. The synaptic transmission is investigated in four different but mutually related flight systems. In these systems, both excitatory and inhibitory synapses can be studied. One merit of these systems is the fact that each system is composed of a limited number neurons, allowing identification of all neurons involved. Thus, study on identified neurons is possible. By taking this advantage, the transmission mechanism at all of the component neurons is studied. Then, the function as a system, i.e., the information-processing mechanism is studied in each system. As the functions of these systems are interrelated, the mechanism for inter-system coordination is also studied. Cell-cultured myo-neural and neuro-neuronal junctions and also synaptic organization developed in culture are studied in conjunction with the above research. Single-gene mutants which affect the synaptic transmission are used to aid physiological experiments. With physiological techniques (conductance measurements, iontophoretic application of putative transmitters, quantum content, equilibrium potential, etc.), determination of transmitter, action of related substances, transmitter release mechanism, and ionic permeability change at the postsynaptic membrane are studied. The result will elucidate the basic mechanism of transmission and information processing and thereby interpret the principle of neurological disease.